This invention relates to packaging machinery, and in particular to a system for enveloping a group of items in plastic film as the items follow a path of travel.
The invention is directed to horizontal form, fill and seal machinery, and particularly to that type of machinery in which items to be packaged are collected in groups, conveyed into a plastic film which has been formed into a tube surrounding the items, and then conveyed with the tube for downstream sealing into discrete packages or bundles. Other applications of the invention are possible, however.
In a form, fill and seal machine, it is important that items be conveyed quickly and accurately in groups for enveloping in the plastic film so that the packages can be regularly and fully sealed in a continuous process. It is imperative that the groups be properly spaced as they enter the tube of plastic film, and if the film has graphics, it is also important that the groups be inserted in the film in registration with the graphics so that after the packages are completed, the graphics are in proper alignment in relation to their contents.
Various types of forming boxes or apparatus have been used in the past to form plastic film into a tube enveloping the items to be packaged. Since the film totally surrounds the items in a continuous tube, compensation must be made to permit the plastic to be formed to surround the path of travel and form about the items to be packaged. To this end, inlet conveyors have been utilized, terminating where the plastic film enters the path of travel (from a side) and envelopes the items. In a typical apparatus, the film and items are then engaged by side pull belts which convey the tube and enveloped items downstream for later sealing. Anytime that different types of belts are employed, synchronization of the belts becomes important to assure proper conveyance of the packaged items. The more different types of belts are used, the more difficult the synchronization becomes.
If a forming box is used to shape the plastic film into the tube, due to the necessary geometry of the forming box, the box must extend at an oblique angle across the path of travel of the items as they enter the film tube. If the items are being conveyed on a flat conveyor, that conveyor must terminate where it first meets the forming box. A downstream conveyor for conveying the tube and the items must also terminate where it meets the forming box. Due to the oblique angle of the forming box, a substantial gap will exist between the conveyors where there is no positive conveyance of the travelling items. While the gap may be acceptable for items which are quite wide and which therefore may bridge the forming box from the upstream conveyor to the downstream conveyor, it is disadvantageous to have such a gap when items smaller than the gap are being packaged.